Link mechanism for pressure casting machines



July 5, 1949. N, LESTER 2,475,394

LINK MECHANISM FOR PRESSURE CASTING MACHINES Filed Feb. 15, 1946 2Sheets-Sheet l INVENTOR. NATHAN LESTER la Z ya@ E' ATTORNEYS l VJuly 5,1949.

, N. LESTER LINK MECHANISM FOR PRESSURE CASTING MACHINES Filed Feb. 13,1946 2 Sheets-Sheet 2 INVENTOR.

NATHAN LESTER ATTORNEYS Patented July 5, 1949 LINK MECHLNISM FORPRESSURE CASTING MACHINES Nathan Lester, Shaker Heights, Ohio, assignorto Lester Engineering Company, Cleveland, Ohio, a corporation of OhioApplication February 13, 1946, Serial No. 647,259

(Cl. i4- 110) 4 Claims.

The present invention relates to improvements in a link mechanism forimparting the final high pressure closing movement to the die plates ofa pressure casting machine. In such machines the die plates carry themold members or die blocks in which the mold cavity is formed when suchdie plates are in closed position and into which cavity the material tobe cast is forced under very high pressure. The die plates musttherefore be held in a closed position under a relatively great forcewhich is sufficient to withstand the casting pressure tending to openthem. Heretofore, toggle link mechanisms having wedge means associatedtherewith have been utilized to acquire this high pressure final closingmovement. However, in these prior devices the wedge means have beenusually engaged only in line contact with one another except at the lastinstant of the nal closing movement, at which time they finally engagein surface contact with one another. Thus, even small forces appliedthrough these Wedge means prior to the last instant of the final closingmovement impart extremely high unit stresses in the engaging portions ofthe wedge means with the result that the wedge means will be deformed orwill score or seize with one another or otherwise be renderedinefficient.

It is one of the principal objects of this invention to provide in sucha toggle link mechanism wedge means which, when engaged, continuouslyengage one another in surface contact during the entire final closingmovement, thereby materially reducing the unit stresses on the wedgemeans and thus minimizing the damage to the wedge means and alsopermitting application of much greater forces during the nal closingmovement.

Another object of this invention is to provide means wherein the area ofsurface contact between the wedge means increases as the closing forceon the die plates increases.

Another object of this invention is to provide simple means foraccomplishing the aforesaid continuous surface contact without requiringthe use of complex universally mounted wedge means.

Additional objects and advantages of the invention will become apparentas the following description proceeds.

To the accomplishment of the foregoing and related ends, said inventionthen comprises the features hereinafter fully described and particularlypointed out in the claims, the following description and the annexeddrawings setting forth in detail certain illustrative embodiments of theinvention, these being indicative, however, of but a few of the variousways in which the principle of the invention may be employed.

1n the drawings:

Fig. 1 is a front elevation view partly in vertical section of thatportion of a pressure casting machine containing the die plate actuatingmechanism, such mechanism having been operated to fully close the dieplates;

ig. 2 is similar to Fig. 1 except that the die plate actuating mechanismhas been operated to fully open the die plates;

Fig. 3 is a vertical cross section of the actuating mechanism takenalong line 3 3 of Fig. 1;

Fig. 4 is a plan view of the actuating mechanism as viewed from the topof Fig. 1;

Figs, 5 and 6 are enlarged views partially schematic of the linkmechanism just prior to commencement of the final closing movement ofthe die plates, and at the last instant of the final closing movement,respectively; and

Fig. 'l is a schematic enlarged view of the link mechanism clearlyshowing the relationship between the wedge means of the link mechanismfor accomplishing the objects of this invention.

Referring now to the drawings, the machine as a whole includes a frame lwhich reciprocably carries a die plate 2 and which die plate, as is wellknown to those skilled in the art, carries a die block engageable anddisengageable with a die block and die plate, not shown, nxedly mountedon the frame l. Reciprocating movement of the die plate 2 is effected bymeans of a hydraulic piston and cylinder assembly 3 having the pistonrod portion 6 connected thereto. The piston and cylinder assembly 3 isprovided with passages i and 5 and by means of suitable valves, notshown, fluid under pressure can be directed at will to either end of thecylinder to move the piston therein in opposite directions. Theconnection of piston rod 6 to the die plate 2 is effected through atoggle link mechanism which linkage is arranged in cooperation with theframe i to effect movement of the piston rod and die plate rapidly inunison during the opening and closing movements, but with very greatrelative movement during the final closing and initial opening move- 3ments to attain the great mechanical advantage necessary in order toeifect nal closing of the die plates with very high pressure.

The toggle linkage comprises links l' and 8 pivotally connected to oneanother and to the piston rod 6 and die plate 2, respectively. As shown,one end of each link 'I is pivotally connected to the die plate 2 abouta pivot pin 9 which passes through the link 1 and through the spaced earportions I on the die plate. Each of the ear portions I0 has a hardenedmetal insert il secured4 thereto in engagement with 'a hardened metalinsert I-'2 secured to each 'link 1. The faces of inserts II and I2which are in engagement with one another are cylindriform with eachpivot pin 9 as an axis. As will become-more apparent as the descriptionproceeds, a shearing,

stress on the pins 9 will be relieved or limited by the bearing orcompressionstress taken. up bythe engagement of these inserts with onean'- other. Each link 'I has a laterally projecting leg iS thereon, theend of which is engageable with a corresponding leg on the other link lto limit the pivotal movement of., the links 'l toward one another. Eachlink 'I is' also provided with two shelf vportions =`I`3, slidablyengageable With'correspending-shelf portions I-'YI in the frame -I. Awear strip-I is secured to each shelf I3 to take up the wear between the-shelf lportions of the links r'l and the frame I.

A plurality o'f links f8' are vpvotally connected about pivot pins I1and I8 to the links-l and to ahead I8, respectively, which head issecured to the .piston lrod. .Hardened metal `inserts 2t 'between thelinks fl-Jandia operate lto relieve or limit "the shearing stress-onpinsI1 as described above in relation to pin eandinserts lfI and I2.

VSecured"to frame I andi to the vouter ends of linksil are'hard'ened-metal'wedge inserts Z'I and 22, respectively. For thelpresent, let `it suffice to say that asthe llinks l'I'.are swungoutwardly about pins '9, the insertsi. and 22` will engage one anotherto effect relative lmovement between the framel and the die plate f2.

As :for the .'generalzoperaition .of the .toggle linkage,letLusassumethatz'die plate 2 is fully opened asshownin Fig; .2. 1nthis-positionlinks .'I are collapsed inwardly Ywith .legs .'IH'fthereofvin' engagement and 'with the shelf portions I3 of 'the links in.engagement with the Ishelf portions I4 inthe 'frame -I.; Now, if1it'.bedesired to move the die plate-2 toward the :right 'toa closedposition into engagement 'with .the l'other die plate, not shown,:pistonrod 6=iscaused to be'rnoved toward the right. In :so doing, the:piston .rod 6 and die plate :2 willmove in Iunisonsby reason lof thefact that links 7 are constrained ,bythe shelf portions SI 4 'from being:swung .outwardly `by the .force appliedto the links-,28. However, assoonzas the die plate-'2 lightly :engages the other die plate and theshelf portions I3 andM vdisengage from one vanother :and v.the inserts2| and 2 2. lare iin the position `shown 'in Fig. .5, .further movementof the piston rod i5. toward-:the right will, throughV thelinks 8, causethe :links 'I to :be swung outplate-2. .The fnalizclosjed.' `positionofpthedie plate. is .attained fwhenthe, links Tf'and-fbearerelationn 4to one another, as shown in Figs. 1 and 6. In Fig. 6, the distancethrough which die plate 2 has been moved relative to the frame I duringthe final closing movement is indicated by the dimension line 30.

To clearly set forth the principal feature of this invention, referencewill now be made primarily to Fig. 7 and also to Figs. 5 and 6 whichschematically show the relation of the surfaces of the inserts 2l and 22to one another and to the axis of pin 9. Inasmuch as the movementbetween frame I` and die plate 2 is relative, the following description,in order to simplify and clarify the same, will proceed on theassumption that frame I is movable and that die plate 2 is fixed. Whenthe inserts 2l and 22 are in the position` shown in Fig. 5 and as shownin full lines in Fig. 7, the axes 23 of the cylindrical faces Z4 and 25of the inserts are coincident but eccentric 'of' the axis 26 'of pin Si.The relative movement between frame I and the die plate is indicated inlamount land direction by the dimension 2? and the straight line 28.Thus, at the attainment of the final closing movement, axis 23 will havemoved to positionA. New, in order that surface 25 will engage surface2li in surface cer;- taot as the linkl rotates about axis 25,'it isnecessary that axis 23 of surface 25 always be coincident with axis23ofsurface 24. From a theoretic standpoint, thiszcan be accompiishedoniy bymoing vaxis 23 of surface 25' in a straight line 28 as does the axis 23`of surface 2t. However, from a practical standpoint',fsuchcan besatisfactorily accomplished by selectingthe axis 2B along a line whichis the perpendicular bisector rof y'the lim 28. In such `case,axis '2'3of surface 25 will move in a circular 'path .29 -of radius equal to thee2- centric'ityvof the axis S23 with respect to the 2t, as the link l is'rotated about axis 25. For

.' small amounts of vrelative movement, the clrcuiar path .2Q-Will atallv times bet veen the `limits o line 28 be so nearly straight that forall practical purposes, axesy 23 ofthe .surfaces 2li and 2:5 will becoincidentrduring movement. of the insert 22 .from'the-solidiline.position 'to the Ldotted line position. Naturally, as the ratio of theeccentricity to .the .amount of. relative vmovement approaches infinity,the path. of the axs which describes facircul'ar `path `will approach astraight line path. v

Tn "an actual machine, :thexrelative movement during the `final:closingmovement is fon Vthe order of 'only .several `thousandths lofaniin'ch iand there fore the error due vtothe theoretical noni-'cncidence iof 'the .axes 23Y can 'be ,disregarded and itcanbefconsidered, as :apractical matter, that surface 25 will'engagesurface 24 .in'surface 'Contact throughout `its "movement v.fromthe solid line position to ther 'dotted line position of Fig. 7. Thus,;it "will .be seen that as l.tim-'closing force increases', .the'area::df'surfaees 2id 'and 25 in contact. likewise .increases.andbecause there is vsurface contact, as` distinguished from linecontact, much greater forces vcan Vbe transmitted to the die plate 2Without vcausing .damage vor excess Wear tothe inserts 121i and 22;

Other imodes of applying 'the principle of the invention maylbeuemployed', change .being made as regards 'the 'detailsdescribed,Vprovided the features stated in :anyfof 'the following claims or theequivalent of such .be 'employed and 'while described with particularreference to its 'use in a Apressure ycastingmachine, .it will. beunderstood that mylimprnyedlinkmeenanism imay 'be used y'in'fconjunction, any: mainline for f'device" wherein it is desired toimpart high pressure relative movement between two relatively movablemembers.

I therefore particularly point out and distinctly claim as my invention:

1. In a linkage mechanism for pressure casting machines and the like,the combination with two relatively movable members of a link pivotallyconnected to one of said members for swinging movement into abuttingengagement with the other of said members, said link and other memberbeing formed with abutting cylindrical surfaces bearing fixed relationto said link and other member respectively, the axes of such surfacesbeing disposed eccentrially of the pivot axis of said link andcoinciding during swinging movement of said link as aforesaid.

2. In a linkage mechanism for pressure casting machines and the like,the combination with two relatively movable members of a link pivotallyconnected to one of said members for swinging movement into abuttingengagement with the other of said members, said link and other memberbeing formed with abutting cylindrical surfaces bearing iixed relationto said link and other member respectively, the axes of such surfacesbeing disposed eccentrically of the pivot axis of said link andcoinciding during swinging movement of said link as aforesaid, the pivotaxis of said link lying on a line perpendicularly bisecting the line ofrelative movement of said members effected by swinging of said link asmeasured by the line of movement of the axes of the abutting surfaces ofsaid link and other member relative to the pivot axis of said link. l

3. In a linkage mechanism for pressure casting machines and the like,the combination with two relatively movable members of a link pivotallyconnected to one of said members for swinging movement to a wedgedposition between said members, said link and the other of said membersbeing formed with abutting cylindrical surfaces bearing xed relation tosaid link and other member respectively, the axes of such surfaces beingeccentric of the pivot axis of said link and coinciding when said linkis in a position with its cylindrical surface adjacent that of saidother member and during movement of said link to a wedged positionbetween said members.

4. In a linkage mechanism for pressure casting machines and the like,the combination with two relatively movable members of a link pivotallyconnected to one of said members for swinging movement to a wedgedposition between said members, said link and the other of said membersbeing formed with abutting cylindrical surfaces bearing xed relation tosaid link and other member respectively, the axes of such surfaces beingeccentric of the pivot axis of said link and coinciding when said linkis in a position with its cylindrical surface adjacent that of saidother member and during movement of said link to a wedged positionbetween said members, the pivot axis of said link lying on a lineperpendicularly bisecting the line of relative movement of said memberseffected by swinging of said link from a position with its cylindricalsurface adjacent that of said other member to a position wherein saidlink is wedged between said members.

NATHAN LESTER.

REFERENCES CITED The following referenlces are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 494,502 Whitacre Mar. 28, 1893638,990 Replogle Dec. 12, 1899 972,689 Gillespie Oct. 11, 1910 2,186,030Lester Jan. 9, 1940

